The past tense with the particle 了
The modal particle 了 has several functions. One of its functions is to express the past tense.
The particle 了 as a past tense marker
The modal particle 了 
is placed at the end of a sentence and expresses the past tense.
is placed at the end of a sentence and expresses the past tense. Examples
我去超市了
I went to the supermarket
wǒ qù chāoshì le
中午我做作业了
I did my homework at noon
zhōngwǔ wǒ zuò zuòyè le
Note that it is not the suffix 了. Let’s compare them:
The suffix 了 is placed after a verb and indicates the completion of an action and a result:
· the result of a trip to the supermarket is buying food;
· the result of a phone call is a telephone conversation.
If the verb is followed by an object, it must be extended.
Examples
他去商店买了一件衬衫
He went to the shop and bought a shirt
tā qù shāngdiàn mǎi le yí jiàn chènshān
The particle 了 is placed at the end of a sentence. It is in the past tense, but it doesn’t specify whether there is any result.
· I went shopping - we just indicate that an action was done, the result is not important;
· I made a phone call - an action was done and it doesn't matter whether we spoke with somebody on the phone or not.
If the verb is followed by an object, the object is usually unextended.
Examples
他去商店买衬衫了
He went to the shop to buy a shirt
tā qù shāngdiàn mǎi chènshān le
When 了 is not used
The modal particle 了 is a past tense marker. However, there are some instances when you cannot use this particle:
1) when an action happens habitually or regularly:
Examples
去年我每天都上汉语课
Last year I had Chinese lessons every day
qùnián wǒ měitiān dōu shàng hànyǔ kè
Pay attention
These sentences have the signal words like 常常 , 偶尔 and 每 .
, 偶尔 and 每 .
2) when actions happen one after another:
Examples
昨天我上午上课，下午去朋友家吃饭
Yesterday morning I was in class. In the evening I went to a friend's house for dinner
zuótiān wǒ shàngwǔ shàngkè, xiàwǔ qù péngyou jiā chīfàn
3) when the action happens over a period of time:
Examples
我回家的时候，妈妈在睡觉呢
When I got home, my mother was sleeping
wǒ huí jiā de shíhou, māma zài shuìjiào ne
4) when a predicate is expressed by a verb that expresses a state. For example:
知道
是
有
When a predicate is expressed by a verb that expresses feelings and emotions. For example:
爱
希望
是
有
When a predicate is expressed by a verb that expresses feelings and emotions. For example:
爱
希望 Examples
以前我喜欢听京剧
I used to like listening to the Peking Opera
yǐqián wǒ xǐhuan tīng jīngjù
我不知道如何处理那个问题
I don't know how to deal with that problem
wǒ bù zhīdào rúhé chǔlǐ nà ge wèntí
5) when there are modal verbs in the sentences. For example:
能
会
会 Examples
他很长时间不能站起
He couldn't stand up for a long time
tā hěn cháng shíjiān bù néng zhànqǐ
In these cases, it is clear from the context that it refers to the past.
Negative sentences in the past tense
In negative sentences in the past tense, the negative adverbs 没 and 没有 are placed before the verb.
and 没有 are placed before the verb. Pay attention
In this case, the particle 了 is omitted. It cannot be used in negative sentences.
Examples
我没有去超市
I didn't go to the supermarket
wǒ méiyǒu qù chāoshì
我没看这本书
I didn't read this book
wǒ méi kàn zhè běn shū
Interrogative sentences in the past tense
Interrogative sentences are formed in the following three ways:
1) using 了吗 at the end of a sentence.
at the end of a sentence.
Examples
你做作业了吗？
Have you done your homework?
nǐ zuò zuòyè le ma
他们给你这个职位了吗？
Did they offer you this position?
tāmen gěi nǐ zhè ge zhíwèi le ma
2) using 没有 after 了 at the end of a sentence.
Examples
你吃饭了没有？
Have you eaten yet?
nǐ chīfàn le méiyǒu
他去医院了没有？
Has he gone to the hospital yet?
tāmen gěi nǐ zhè ge zhíwèi le méiyǒu
3) using reduplication of verbs and the negative adverb 没. If a sentence has an object, the object is only stated once after the second verb.
Pay attention
In this case, 了 is omitted.
Examples
你吃没吃饭？
Have you eaten yet?
nǐ chī méi chīfàn
他去没去医院？
Has he gone to the hospital yet?
tā qù méi qù yīyuàn